1. Technical Field
The present invention relates to a drive motor for driving a cutting tool of a dental handpiece, more particularly to a cooling structure of the motor.
2. Related Art
Motor-driven type dental handpieces include a tooth cutting handpiece, a surgical (or implant) handpiece and a root canal treatment handpiece, and the like. The tooth cutting handpiece is used for cutting a tooth, the surgical handpiece is used for drilling a hole into a jawbone and for fixing an implant in a dental implant operation, and the root canal treatment handpiece is used for cutting or enlarging a root canal.
In the motor-driven type dental handpiece, as illustrated in FIG. 9, a handpiece 200 includes a first rotation shaft 202, which rotates in engagement with a drive shaft inside the top end connecting part 201 of an electric motor M; a second rotation shaft 203, which is tilted with respect to the first rotation shaft 202; a first gear train 204, which links the first rotation shaft 202 and the second rotation shaft 203; a tool rotating shaft 205 orthogonal to the second rotation shaft 203; and a second gear train 206, which links the second rotation shaft 203 and the tool rotating shaft 205. The first and second rotation shafts 202, 203, the first gear train 204, the tool rotating shaft 205, and the second gear train 206 construct a rotation transmitting mechanism as with, for example, JP 2005-342403 A.
The method for cooling a motor of each of these motor-driven type dental handpieces is different from the others depending on the type of the handpiece. The tooth cutting handpiece comprises a feeding path, through which air for cooling components of the handpiece including the motor (hereinafter, called as “cooling air”) is fed for suppressing heat generation due to high speed rotation of the cutting tool. The cooling air fed through a connection hose passes through the inside of both the motor and the handpiece, and is discharged outside from the top end of the handpiece where the cutting tool is mounted as with, for example, JP 2005-342403 A and 2001-29361 A.
On the other hand, in the case of the surgical handpiece and the root canal treatment handpiece, cooling air is not used for the sake of avoiding unwanted bacteria included in the cooling air to be fed to the affected area, and the motor is upsized for securing its thermal capacity or the motor is cooled by use of a fan as with, for example, JP 2007-267913 A.